Stephen Kosslyn's work on mental imagery was very influential on my thinking about learning in the 1980s. Here Kosslyn and Samuel T. Moulton post a book chapter (in image scans - hard to read) summarizing the recent (2009) work in the field. This is hard research, drawing directly from experimental results. There are some good take-homes. For example, they write, "much of what we know consists not of facts or events that we can consciously recollect but rather of ways to behave or tendencies to process information in certain ways in certain situations." Moreover, "mental practice involves creating images you can imitate... imitation is a key element that underlies mental practice." The article goes on to describe the neural basis for imitation, and describes mental practice step by step (basically describing practice and reflection). Via Eide Neurolearning. If you want to see this in action, watch this video of a child playing a ukulele and singing - behaviour that is a clear example of this type of imitative learning.